Wells are generally drilled into subsurface rocks to access fluids, such as hydrocarbons, stored in subterranean formations. The formations penetrated by a well can be evaluated for various purposes, including for identifying hydrocarbon reservoirs within the formations. During drilling operations, one or more drilling tools in a drill string may be used to test or sample the formations. Following removal of the drill string, a wireline tool may also be run into the well to test or sample the formations. These drilling tools and wireline tools, as well as other wellbore tools conveyed on coiled tubing, drill pipe, casing or other means of conveyance, are also referred to herein as “downhole tools.” Certain downhole tools may include two or more integrated collar assemblies, each for performing a separate function, and a downhole tool may be employed alone or in combination with other downhole tools in a downhole tool string.
Formation evaluation may involve stationing a downhole tool at different locations within a well and measuring formation pressures at those locations. In some instances, an intake of the downhole tool can be hydraulically coupled to a formation and a pretest may be performed to measure the formation pressure and mobility. More specifically, during a pretest, fluid can be drawn from the formation into the tool through the intake by creating a negative pressure differential between the formation and the tool interior (referred to as a drawdown), and formation fluid drawn into the tool causes the pressure to gradually increase (referred to as a buildup) toward the formation pressure. Pumps within the tool can be used to initiate a drawdown and to route fluids within the tool. The measured formation pressures can facilitate reservoir characterization and be used to optimize subsequent activities at the well.